Patch to add new functionality

This patch changes Vocabulary per book so that any vocabulary can be used with any book or content_type. The Vocabulary tab has been re-written as a form to associate/disassociate vocabularies as well as create new ones.

I have tested most of the functionnality and it works, though there are some issues.

Tested

1. Create new vocabulary and associating with a book
2. Associate an existing vocabulary to a book
3. Disassociate a vocabulary from a book
4. Associate the same vocabulary to multiple books
5. Dissassociate a vocabulary associated to multiple books from one book
6. Update an existing site with book_vocab and some books with vocabularies

Issues

1. When a vocabulary is disassociated from a book, the book nodes keep the terms associated to that vocabulary, so in taxonomy, the vocabulary terms still point to the book nodes for example. Also, if the vocabulary is re-assigned to the book, all the book nodes will show their terms.
2. Because of the AJAX used by the book module for assigning a node to a book, the associated vocabularies will not be displayed if the user changes the book while editing/creating a book node.
3. If the book_vocab module is uninstalled, all the vocabularies remain.